The present invention relates generally to an automatic clothes dryer.
Automatic clothes dryers are well known and provide various control mechanisms for applying heat and terminating the operation of a tumbling action of the clothes receiving drum once clothes are detected to be dry. It is known to utilize moisture sensors and humidity sensors for detecting when the clothes load is dry and for estimating the remaining time before the clothes load will be dry.
A typical motor used for rotating dryer drums is a split phase induction motor which has a start winding and a main winding. When the dryer is started, a centrifugal switch on the motor shuts off the start winding when the motor reaches a speed high enough to sling out a pair of fly weights on its actuator. Then, a normally open contact on the switch closes. Once the switch is closed, the motor will continue in operation until some other event occurs, such as a detection that a certain dryness level has been achieved by the moisture sensors, a certain pre-selected time period selected by the user has elapsed, or the door to the dryer drum is opened. Any one of these events will open a different switch, thereby removing power from the motor and terminating the tumbling action.
In those dryers where an estimated remaining time to complete the drying cycle is displayed, this estimated time is determined only after the dryer has been operating for at least several minutes. It would be an improvement in the art if a display of remaining time could be provided at approximately the same time that the drying cycle is started.
The present invention provides an arrangement for detecting the size of the load presented in the dryer drum at the initiation of the drying cycle which can be used to estimate the time remaining for the drying cycle.
Dryers with electronic controls can utilize this remaining time to provide the user with an early estimate of how long it will take to dry the clothes. By estimating the mass in the dryer, a proportion can be used to arrive at an estimated drying time.
A method of determining an estimated drying time of a fabric load in an automatic clothes dryer is provided wherein the dryer utilizes a motor including a centrifugal switch which closes upon the motor achieving a predetermined speed at a start of the motor. This method includes detecting the start of the dryer motor and simultaneously starting a timer. A voltage of the line current used to power the motor is determined, the closure of the centrifugal switch of the motor is detected and the timer is simultaneously stopped to achieve a start time. The start time and the predetermined voltage are used in a predetermined formula for the particular dryer to calculate an approximate mass of the fabric load in the dryer. To utilize this calculated mass, it can be inserted into a formula to approximate a drying time for the fabric load and this approximate drying time can be displayed on a display associated with the dryer less than one second after the start of the drying cycle.
In an embodiment of the invention, an LED is placed in the line conductor for the motor and an optical pickup is used to detect energization of the LED to determine a start of the dryer motor. In an embodiment of the invention, detecting the closure of the centrifugal switch comprises an LED in a line closed by closure of the centrifugal switch and utilizing an optical pickup to detect energization of this LED. In a different embodiment of the invention, detecting the closure of the centrifugal switch includes monitoring a voltage of the power supply and stopping the timer when a change in the monitored voltage is greater than a predetermined amount.